Automatic switch



Patented Sept. 29, 1953 UNITED STATES PATENT OFFICE AUTOMATIC SWITCHJames M. Wallace and An McKeesport, Pa., assi Electric Corporation,

17 Claims. 1

This invention relates to systems for the distribution of electricalpower as well as switching mechanism therefor, and more particularly toa novel arrangement for automatically energizing the system by sections.

In electrical distribution systems wherein the load density isrelatively high and comprises for example, a larger number of loaddevices which require high inrush currents for starting, considerabledifiiculty has been heretofore experienced in reenergizing the systemfollowing a main or bus fault or similar outage which persists for arelatively long period of time. This condition results from the factthat during deenergization of the system, due to the outage, the motordriven automatic devices such as refrigerating systems, air compressors,pumps and the like, will be conditioned for operation, and thus thediversity factor of the system will be eliminated. It will be readilyunderstood that under such conditions, the current required after theoutage will be several times normal load values and this may persist fora substantial period of time. As a result, the protective devicesassociated with the system will operate and render it impossible to pickup the load.

It is accordingly, one of the objects of the present invention toprovide an electrical distribution system and switch mechanism thereforwhich is so arranged and constituted as to avoid the objections anddisadvantages outlined above.

Another object is to provide a system of the foregoing character whichis constructed in such a manner that reenergization thereof, after anoutage, will occur by sections, each section being automaticallyenergized a predetermined time interval after the preceding section.

Still another object is to provide in an electrical distribution system,a novel arrangement of automatically operable sectionalizing switcheshaving time delay characteristics, the construction being such that uponreestablishment of service following an outage, the various loadsections will be reenergized at successive time intervals beginning atone end of the system and continuing throughout the length thereof.

Another object resides in the provision of a novel sectionalizing switchconstruction for a system of the above type, so arranged as to preventopening thereof during a temporary fault but insuring opening operationwith a time delay interval should the fault persist.

A further object is to provide in a. switch construction of the abovecharacter, a novel arrangement including time delay means for openingthe drew W. Edwards, East gnors to Westinghouse East Pittsburgh, Pa., acorporation of Pennsylvania Application November 19, 1948, Serial No.60,862

switch upon the persistence of a fault, and including also, time delaymeans for closing the switch in response to reenergization of thepreceding load section.

A still further object is to provide a novel sectionalizing switchconstruction which is highly efiicient in operation, includes relativelyfew parts, and is economical to manufacture.

The above and other objects and novel features of the invention willappear more fully hereinafter from a consideration of the followingdetailed description when taken in connection with the accompanyingdrawing which is illustrative of one form of the invention. It is to beexpress- 1y understood however, that the drawing is utilized forpurposes of illustration only and is not to be taken as a definition ofthe limits of the invention, reference being had for this purpose to theappended claims.

In the drawing, wherein similar reference characters refer to similarparts throughout the several views:

Figure 1 is a. substantially central sectional view of a sectionalizingswitch constructed in accordance with the principles of the presentinvention, and

Fig. 2 is a diagrammatic view of a transmission circuit having aplurality of load sections and sectionalizing switches associatedtherewith.

Referring more particularly to Fig. 2, the present invention isillustrated therein as including a transmission circuit [0, providedwith a suitable source of power such as transformer l2, and including aconventional circuit protective device such as an automatic reclosingcircuit breaker M of a well known type which, upon the occurrence of anoverload condition, recloses a predetermined number of times and isfinally locked out in the event that the condition persists. Uponclearing of the fault, the breaker I4 is manually closed to restoreservice. As shown, a plurality of sectionalizing switches l6, l8 and 20,of similar construction, are connected with the circuit and serve tosectionalize the latter into load sections 22, 24, 26 and 28. With suchan arrangement, it will be readily understood that energization of theload section 22 depends upon the closure of the breaker l4, whileenergization of the load sections 24, 26 and 28 depends upon thesuccessive closure of the switches l6, I8 and 20.

The novel sectionalizing switch of the present invention is moreparticularly illustrated in Fig. 1 and includes a casing 30, preferablyof metal, having line and load terminals 32 and 34 supported in bushings33 and 35 of insulating material such as porcelain, from a cover 36, andhaving also a voltage terminal 38 connected to ground and supported inan insulating bushing 39 passing through the casing wall. In theposition shown, the switch is in series in the circuit wherein linecontact 40, secured on the inner end of load terminal 32, is connectedwith load contact 52, which is secured on the inner end of load terminal34, by a contact element or bar 44. The latter is actuated in oppositedirections to close and open the circuit, by a magnetizable core itcooperable with a solenoid winding Q8, and the energization of thelatter is effected by means of a control circuit 50 which includes thesecondary winding 52 of a transformer 54, the latter being connectedthrough leads 56 and 58 with terminals 32 and 38 respectively, and thusconstituting a source of power for the control circuit it. From theforegoing, it will be seen that when circuit 50 is energized, thesolenoid winding 58 will likewise be energized to maintain the parts 46and 4 in the position illustrated. On the other-hand, should the circuit50 become deenergized, the core 26 will drop and effect an opening ofthe separable contacts constituted by the bar it and contacts so and 42.

The control circuit 50, in addition to the fore going elements, alsoincludes a time delay relay 60 which functions to energize the winding:38 a predetermined interval of time after energization of thetransformer 56. As shown, the relay 69 includes a movable core 63carrying a contact element St which at its uppermost positioncompletes'a circuit from one side of the solenoid winding 48 to one sideof the transformer secondary winding 52 by way of conductor 66, contact68, contact element Ei i, contact it and conductor l2. The time delayaction of the relay 69 in bridging contacts 68 and i is secured throughthe use of a dashpot construction "it which is associated with the core63, and so constructed and arranged as to close the contacts 68 and it apredetermined time interval after energization of the winding 62, whileallowing proinpt disengagement of these contacts upon deenergization ofsaid winding. From this construction, it will be appreciated that thesolenoid winding d8 will be cleenergizedimmediately upon deenergizationof the transformer 54 and the dropping out or relay 66. On the otherhand, upon reenergization of the transformer d, the energi'zation of thesolenoid winding 48 will be delayed for the time interval required forthe contacts 618 and iii to close.

One of the important features of the present invention resides indelaying the disengagement of bridging contact 46 from contacts all, d2when a fault occurs, for a time interval sufficient to enable thebreaker Hi to undergo its complete cycle of reclosing operations. Thus,if the fault is of a temporary nature, and is cleared before completecycling of the breaker, the contacts 40, 42 and M will remain closed. Onthe other hand, if the fault persists and the breaker it is eventuallylocked out, the contact 44 will open after a time delay interval. Inorder to secure the foregoing operation, the core 46 is mounted on thelower end of a piston member 4'1 of nonmagnetic material, preferably ofan insulating connection with the upper portion of piston member i! asit is slidably mounted in a bore provided in the outer end of pistonmember 41. Rod 18 has a head 86 at its inner end which limits lostmotion of the rod by engagement with the inner end of bore 80 at oneextreme of relative movement, and with a cover SI for the bore at theother extreme. Rod 18 is resiliently urged as by a coil compressionspring 82, telescoped over the rod and reacting between contact bar 44and cover 8|, in a direction tending to move rod 18 and piston member 41apart, and thus to maintain engagement between the contact bar as andthe contacts MI and 42 when solenoid coil 418 is energized. With such anarrangement it will be readily seen that when the solenoid winding 38 isdeenergized, the core 36 will move slowly downwardly, due to the dashpotaction of piston member if in the chamber 16, and the contact 4'4 willbe held closed due to the expansion of the spring 82. Uponreenergization of the winding 23, the core 46 will be moved upwardly tothe position illustrated. This operation would occur during thesuccessive reclosing operations of the breaker id, and it will beobserved that the sectionalizing devices l6, I8, 20 will not then openthe circuit. however, should the breaker l become finally locked out,thus causing deenergiz ation of the winding 68 for a substantial timeperiod, the core 46 will slowly drop to a position where the interior ofthe chamber i6 coinniuiii catcs with the atmosphere by way of aplurality of slots 8 3 formed on the piston member il. When this occurs,the-core t6 suddenly drops downwardly and the cover 3! engages head 86of rod '58 to positively disengage the contact bar it from the contacts40 and 42.

It has heretofore been pointed out that during cycling of the reclosingcircuit breaker Hi, the time delay relay 6!} will be alternately en'-ergiz ed and deenergized. In order to avoid dis-' engagement of thecontact bar 44 from the contacts 4d and 42, durin the time intervalrequired for closure of the contacts 68 and 70 when the relay Ell isreenergized, a novel arrangement is provided for insuring energizationof the solenoid winding 48 immediately upon reenergization of thesecondary winding 52 of the transformer 5%. As shown, such arrangementincludes a circuit 88, connected parallel With the contacts 68 andlfl,and having a thermally responsive switch 90 therein. More particularly,the switch 93 is preferably of the bimetal type including a contactcarrying bimetal element 92, which when heated to a predetermineddegree, flexes downwardly to engage a fixed contact 94. A heating coil96, connected between the contact 68 and the conductor 66 of circuit 50,is arranged closely adjacent the bimetal element 92 in orderto heat thelatter and cause a circuit closing operation thereof in the mannerindicatedl It is pointed out that the switch 9Q possesses sufficientthermal capacity as to remain closed throughout an open circuitcondition existing during the cycling operations of the breaker Hi Whena fault occurs in the transmission circuit. Thus, notwithstanding thetime delay action of the relay 6B, in closing contacts, threenergization of the transformer secondary Winding 52 will immediatelycause reenergization of the solenoid winding, 38 by way of the seriescircuit including the conductor 12, stationary contact 94, bimetalcontact-carrying arm 32, heating coil 9.5, conductor 65, winding 48 andsecondary 52, and the contacts 40, 42

and 44 will hence remain in engagement during successive reclosings ofthe breaker [4.

In operation, it will be assumed that the transmission circuit HI andthe sectionalizing switches l6, l8 and represent a portion only of asystem for the distribution of electric power. With the circuit innormal operation, the breaker l4 and the sectionalizing switches are allclosed and the system derives the complete advantages of the diversityfactor of the load. As soon however, as an overload condition occurs inthe circuit, the reclosing circuit breaker l4 will immediately start itscycle of opening and reclosing operations. Should the fault be temporaryand thus cleared before the cycle is completed, the breaker will remainclosed after one of its automatic circuit closing operations. During thecycling of the breaker all of the sectionalizing switches Will remainclosed for the reasons stated.

The latter will however, with a time delay action, open in order tosectionalize and isolate the various load sections 22, 24, 26 and 28 inthe event that the fault is permanent and the breaker l4 becomes finallylocked out. After the fault is cleared and the breaker I4 is reclosed,the load sections 24, 26 and 28 are reconnected in the circuit atsuccessive time intervals in order to obtain a diversity factor.

More particularly, and with the switch It in the position illustrated inFig. 1, it will be understood that as the energization of thetransformer 54 is periodically interrupted through the cycling of thebreaker I4, the contact bar 44 will not become disengaged from thecontact and 42.

Maintenance of the circuit from terminal 32 to y" terminal 34, underthese conditions is assured through the time delay action secured by thedashpot comprising parts 4! and "I6, and through the action of spring 82as the core 46 descends during open circuit periods. Periodicreenergization of the winding 48 in timed relation with thereenergization of the transformer 54 is assured through the use ofcircuit 88 including the bimetal switch 90 and this acts to return core46 toward the position shown in Fig. 1. In the event, however, that thebreaker I4 or other circuit protective device is finally locked in openposition, all of the sectionalizing switches l5, l8 and 20 will openwith a time delay action, in order to sectionalize the load sections 22,24. 26 and 28 and condition the circuit for reconnection in a novelmanner as service is reestablished.

For example, and referring to Fig. 1, when the transformer 54 becomesfinally deenergized, all current flow to the solenoid winding 48 will beinterrupted and the core 46 will slowly descend in the dashpot chamber16, and the spring 82 will expand and maintain the contact bar inengagement with the contacts and 42. As soon however, as slots 84establish communication between the chamber 16 and the atmosphere, thecore 46 will drop suddenly and will positively disengage the contacts.

As soon as the fault has been cleared, and the transmission circuit isto be reestablished, it will be understood that the present inventionprovides a novel method and arrangement for energizing the various loadsections at successive time intervals. Thus, as the protective device [4is closed, service only to the load section 22 is immediatelyreestablished. It will be readily understood that due to the outage, theinitial current demanded by the section 22 may be several times the loadcurrent, but this is much less 6 l than the total which is demanded byall of sections 22, 24, 26 and 28. After a time interval however, thehigh starting currents decrease and finally the load current assumes anormal value and the advantages of the diversity factor of the load arerealized.

Simultaneously with the energization of the load section 22, thetransformer 54 of the switch [6 is energized in order to activate threlay 68 of the switch I 6. Due to the dashpot 14 which is associatedwith the core 63 of this relay, a time delay interval will occur beforethe contact member 64 bridges the contacts 68 and 10 to energize thesolenoid winding 48 to cause terminal 32 to be connected with thterminal 42 through the contact bar 44. Such time delay interval ispreferably such that the load current in the preceding load section 22has decreased to substantially normal value before the member 54connects contacts 68 and 10.

From the construction provided, it will be clear that as soon as theterminals 32 and 34 of the switch It are connected, the load section 24and the transformer 54 of the sectionalizing switch l8 will beenergized. Here again the latter will close to energize the load section26, only after a time delay interval has occurred sufficient to enablethe load current demanded by the section 24 to decrease to asubstantially normal value. In like manner, the energization of the loadsection 28 will be delayed, through the operation of the switch 20. Itwill be understood that any desired number of sectionalizing switchesmay be employed, depending of course upon the character and arrangementof the load sections of the system.

While it is believed that the construction, operation and advantages ofthe invention are readily apparent from the foregoing, it is desired toset out here, a specific example of the manner in which the inventionmaterially improves the operation of existing systems of distribution.Referring to Fig. 2 and assuming that the normal load current for theentire system is 400 amperes or amperes per load section, it has beenfound in actual practice that the initial starting current after asustained outage may be as high as 400 amperes per load section orapproximately 1600 amperes for the system. Such initial load currentdecreases to the normal value in approximately 15 minutes, depending ofcourse upon the character of the load. In the event that thesectionalizing switches of the present invention are employed and arearranged to energize each succeeding load section approximately 15minutes after energization of the preceding load section it will bereadily seen that the maximum current flow occurs when the section 28 isenergized. Such maximum current will be 300 amperes plus 400 amperes or700 amperes which value will decrease to 400 amperes in approximately 15minutes. Should the entire system be energized at once, the initial loadcurrent would be 1600 amperes, more than twice that encountered when thesystem is used with the switches of this invention. With the use of thepresent invention, protective relays associated with the various loaddevices are entirely adequate because of the relatively low value of thestarting current after an outage. Where the entire system is energizedat once however, such relays would be entirely inadequate if the relaysare selected to protect the system during normal operation.

The present invention thus aifords a highly efiicient arran ement forseetitiiaiisms arises mission line in such a mariner as to apply seetioiis er the load at successive time intervals when reestablishingservice following an outage;

While one form of the invention has been iilustrated and describedherein with considerable particular ty, it will be readily understood bythose skilled in the art that modifications may be resorted to withoutdeparting from the spirit of the invention. Reference will therefore behad to the a ended claifns for a definition 6f the liihits of theiiiiientifiz We claim as our invention:

1; An automatic switch havinga line terminal and a was temiiiim forccmiesiic'n to adjacent load sections of a distribution circuit havin aprotective device to successively automatically open and recios'e' thecircuit a predetermined number of times and to thereafter remain openupon the persistence of an overload condition; said switch includingmeans for opening the latter only a predetermined time interval afterdisap pearance of voltage and current on said per: minals which intervalairtime is greater than that between any of the aforesaid successivecirc'uit opening and reclosiiig operations of said protective device,whereby said switch will open only after final opening of the circuit bysaid protective device, andmeans for closing said switch a predeterminedtime interval after a pearance of voltage on said line terminal so as tobe adapted to connect the load section remote from the protective deviceto the oircuit a predetermined time interval after closing or saidprotective device and after retrieval of the overload condition. 7

2. An automatic switch having a of terrninals adapted to be connected toadjacent load sections of an electrical distribution circuit to connectsaid sections in series circuit relation, said switch includingseparable contacts and a so lerioid for separating and engaging thecontacts, control circuit means for controlling said solenoid, meansass'oeiated with said circuit means and responsive to appearance ofvoltage on one of said terminals a short time after disappearance ofvoltage from said terminals to instanta neously energize said solenoidand close the contacts, and other means associated with said cir cuitmeans and responsive to appearance of voltage on said one of saidterminals a longer time after disappearance of voltage on said oneterminal for delaying the action or the solenoid in closing saidcontact-s.

A sectionalizing switch comprising a inov ably mounted control memberhaving a contact engageable with a fixed contact, a solenoid having acore movable in opposite directions as the solenoid is energized anddee'ner'gized, means including a lost motion connection between the coreand control member to positively move the latter to separate thecontacts upon the taking up of said lost motion connection as the coremoves in one direction, resilient means associated with the core andcontrol member to urge the latter in 'a direction to maintain engagementbee tween the contacts during the taking up of said lost motionconnection as the core moves inthe opposite direction, and a dashpot forretarding the movement of the core as the latter moves in said onedirection to take up said lost motion connection, and time delay meansresponsive to voltage on the circuit to energize said solenoid means apredetermined time after the ap ear ance of voltage on said circuit.

' said relay.

3 4; A sectionalizing switch comprising separable contacts, a solenoidhaving a core movable in opposite directions to separate andeng'age saidcontacts, a circuit ior'c'oritroiling the energizetion anddeener'g'ization of said solenoid and in eluding a relay having a membermovable to openand close the circuit, means for energiz ing anddeenergizing said relay, means for de laying the closing of the circuitfor a definite time interval after the energiz'ation of said relay, andmeans including a second circuit for energizing said solenoid uponenergization of 5.- A sectionallzing switch device comprising separablecontacts; current responsive means having a movable member to separateand e'ri gage said contacts, means associated with said member to delaythe separation of said contacts for a predetermined time intervalrciiow= ing the interruption of current flow to said corrent responsivemeans, and means for controlling the application of current to saidciirrent responasive means eoriipr-ising a control circuit, means forenergizing and dee'nergiz'ing' said control circuit, a time delay switchfor establishing a cur rent flow to said current responsive means apredetermined time interval after ehsrgization of said control circuit,and a second control on edit connected in parallel with said time delayswitch for establishing a current flow to said current responsive meansimmediately upon energization of the first named control circuit andarranged to be closed in response to now of current in the first controlcircuit andto open a predetermined time interval after deenergiza= tionof said first control circuit;

6. A sectionalizing switch device comprising separable contacts, asolenoid having a movable core for controlling the separation andengage= ment of the contacts, circuit means for com trolling saidsolenoid including a first circuit having a switch therein and a secondcircuit corrne'cted in parallel with said switch and includ= ing athermal responsive switch, a relay asso= ciated with said first circuitand including a member movable to close said switch, means to energizethe relay and said second circuit, means cooperating with said member toprovide a time delay interval in the closing of said switch, andelectrical heating means in the first circuit in ranged in thermalrelation with said thermal responsive switch to close the latter tocomplete said second circuit, said thermal responsive switch beingconstructed and arranged to remain closed for a predetermined timeinterval after deenergileation of said relay.

7. An automatic switch having a line terminal and a load terminal forconnection to adjacent load sections of a distribution circuit having aprotective device to successively open and recl'ose the circuit apredetermined number of times and to thereafter remain open upon thepersistence of an overload condition, said switch including sepa= rablecontacts which are biased apart, electro= responsive means for closingsaid contacts and maintaining them closed when energized, time delaymeans preventing separation of said con= tacts for a time greater thanthe open circuit time between successive operations of said protecti'vedevice in a cycle of operation, voltage responsive time delay meansfor-energizing said Contact closing means a predetermined time afterappearance of voltage on said line to close said contacts, meansresponsive to Zero voltage on said line te'niium to open a circuit apredetermined time after the occurrence of zero voltage, and

means responsive to energization of said contact closing means by saidvoltage responsive means to close another energizing circuit throughsaid zero voltage responsive means, so that the contacts of said switchwill not Open during a cycle of operation of said protective device butwill open only after the last operation of any such cycle of operation.

8. An automatic switch having a line terminal and :a load terminal forconnection to adjacent load sections of a circuit having a protectivedevice to successively open and reclose the circuit a predeterminednumber of times and to thereafter remain open upon the persistence of anoverload condition; said switch including separable contacts which arebiased apart, electroresponsive means for closing said contacts andmaintaining them closed when energized, time delay means preventingseparation of said contacts for a time greater than the open circuittime between successive operations of said protective device in a cycleof operation, means responsive to zero voltage on said line terminal toopen an energizing circuit for said electro-responsive means apredetermined time after the occurrence of zero voltage, and other meansresponsive to voltage on said line terminal for establishing anenergizing circuit through said zero voltage responsive means, so thatthe contacts of said switch will not open during a cycle of operation ofsaid protective device but will open only after the last operation ofany such cycle of operation.

9. An automatic switch comprising, separable said electro-responsivemeans a predetermined time after the appearance of voltage on saidcircuit, second time delay means preventing separation of said contactsfor a predetermined time following disappearance of voltage from thecircuit, and means responsive to energization of said electro-responsivemeans for conditioning a second voltage responsive means to energizesaid electro-responsive means instantaneously upon the occurrence ofvoltage on the circuit, and said second voltage responsive meansincluding means for delaying resetting thereof to a non-voltageresponsive condition, so that said electro-responsive means isinstantaneously energized following an open circuit condition of shortduration, but its energization is delayed following an open circuitcondition which is of longer duration than the resetting period of saidsecond voltage responsive means.

10. A switch comprising, separable contacts which are biased apart,solenoid means for closing said contacts and holding them closed whensaid solenoid means is energized, said solenoid means having lost motionwith respect to said contacts, resilient means reacting between saidsolenoid means and contacts to be stressed when said solenoid means isenergized and said contacts closed, time delay means governing movementof said solenoid means at least in the contact opening direction so thatsaid contacts will remain closed a predetermined time followingdeenergization of said solenoid means, and time delay means responsiveto voltage on the circuit to energize said solenoid means apredetermined time atfer the appearance of voltage on said circuit.

11. A switch comprising, separable contacts which are biased apart,solenoid means for closing said contacts and holding them closed whensaid solenoid means is energized, said solenoid means having lost motionwith respect to said contacts, resilient means reacting between saidsolenoid means and contacts to be stressed when said solenoid means isenergized and said contacts closed, time delay means governing movementof said solenoid means at least in the contact opening direction so thatsaid contacts will remain closed a predetermined time followingdeenergization of said solenoid means, time delay means responsive tovoltage on the circuit to energize said solenoid means a predeterminedtime after the appearance of voltage on said circuit, and meansresponsive to energization of said electro-responsive means forconditioning a second voltageresponsive means to energize said solenoidmeans instantaneously upon the occurrence of voltage on the circuit, andsaid second voltage responsive means including means for delayingresetting thereof to a non-voltage responsive condition, so that saidelectro-responsive means is instantaneously energized following an opencircuit condition of short duration, but its energization is delayedfollowing an open circuit condition which is of longer duration than theresetting period of said second voltage responsive means.

12. An automatic switch having a pair of terminals adapted to beconnected to adjacent load sections of an electrical distributioncircuit to connect said sections in series circuit relation, said switchincluding separable contacts which are biased open andelectro-responsive means for closing the contacts, control meansresponding to the presence of voltage on one line terminal forenergizing said electro-responsive means comprising one means responsiveto a relatively short absence of voltage from said one terminal forinstantaneously energizing said electro-responsive means and a timedelay means responsive to the appearance of voltage on said one terminalfor energizing said electro-responsive means only after the lapse of apredetermined time.

13. An automatic switch having a pair of terminals adapted to beconnected to adjacent load sections of an electrical distributioncircuit to connect said sections in series circuit relation, said switchincluding separable contacts which are biased open andelectro-responsive means for closing the contacts, control meansresponding to the presence of voltage on one line terminal forenergizing said electro-responsive means, said control means beingbiased to reset and open the energizing circuit for saidelectro-rcsponsive means in the absence of voltage on said one terminal,and said control means including timing means dependent on the length oftime voltage is absent from said one terminal for varying the timerequired by said control means to energize said electro-responsive meanswhen voltag reappears on said one terminal.

14-. An automatic switch having a line terminal and a load terminal forconnection to adjacent load sections of a distribution circuit having aprotective device to successively automatically open and reclcse thecircuit a predetermined number of times and to thereafter remain openupon the persistence of an overload condition; said switch being biasedopen, means responsive to line voltage on said terminals to preventopening of said switch by its opening bias including time delay meanspermitting opening of the switch a predetermined time interval afterdisappearance of voltage and current on said terminals which interval oftime is greater than that time interval afterclosing of said protectivedevice and after removal of the overload condition.

15,, A switch comprising, separable contacts which are biased apart,solenoid means for closing said contacts and holding them closed whensaid solenoid means is energized, said solenoid means having lost motionwith respect to said contacts, time delay means governing movement ofsaid solenoid means at least in the contact opening direction whiletaking up said lost motion so that said contacts will remain closed apredetermined time following deenergization of said solenoid means, andtime delay means responsive to voltage on the circuit to energize saidsolenoid means a predetermined time after the appearance of voltage onsaid circuit.

16. A switch comprising, separable contacts which are biased apart,solenoid means for closing said contacts and holding them closed whensaid solenoid means is energized, said solenoid means having lost motionwith respect to said contacts, resilient means acting on said solenoidmeans to be stressed when said solenoid means is energized, time delaymeans governing movement of said solenoid means at least in the contactopening direction while taking up said lost motion so that said contactswill remain closed a predetermined time following deenergization of saidsolenoid means, and time delay means responsive to voltage on thecircuit to energize said solenoid means a predetermined time after theappearance of voltage on said circuit.

17. A sectionalizing switch comprising separable contacts, a solenoidhaving a core movable in opposite directions to open and close saidcontacts, said core b ing movable relative to said contacts in a circuitopening direction a predetermined amount before causing opening of saidcontacts, means preventing movement of said core relative to saidcontacts in a circuitclosin direction prior to engagement of saidcontacts, circuit means for energizing said solenoid when the circuitmeans is closed and for deenergizin said solenoid when the circuit meansis opened to correspondingly cause movement of said core to close oropen said contacts, means for delaying the movement of said corerelative to said contacts in a direction to open the contacts when saidcircuit means is opened and said solenoid is deenergized, means movableto close said circuit means, and means associated with said movablemeans for delaying the movement of the latter to close the circuitmeans.

JAMES M. WALLACE. ANDREW W. EDWARDS.

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